Stress is the number one consequence of keeping your pet in enclosures that do not provide the ideal environment. It is very common in reptiles, amphibians, and many small mammals due to its sensitivity to the environment. Owning a stressed animal can lead to a bundle of other long-term issues. Some Reptile accessories may be too small for your pet to exercise appropriately or to do whatever they want.
You always want to create a habitat that is as representative of their natural habitat as possible. For reptiles, certain case accessories are extremely important in helping them feel secure and don't seem to be easy targets. The ability for an enclosure to hold a constant temperature is also too important and cannot be stressed enough. Many animals depend on certain temperatures to regulate certain habits necessary for their survival.
The next consequence of keeping pets in inappropriate enclosures is health issues. It usually comes with prolonged stress. Like humans, many animals can develop several health problems from stress such as respiratory infections, eating disorders, and mobility problems. As the owner, you are responsible for the size, cleanliness, and many other variables of your animal's enclosures.
Strange behavior is the last major problem associated with pets living in inappropriate enclosures. This can include aggression, biting, excessive chewing, licking, feather plucking, and other means of self-mutilation. Aggressive behavior is a great danger to the animal as well as to anyone who comes in contact with it.
Several species of reptiles, such as the Green Iguana, have been known to attack and inflict serious injury when they are not happy. Caged companion animals in a small enclosure can be extremely territorial and may harm anything that lives with it.